Backscattering values across multi temporal S1 images

Microwave Toolbox
#1

I stacked 4 S1 GRD data but i find out, at the same location, the dB values ranging from -8.xxx dB to -21.xxx dB. Confusingly, acrosss these 4 data, there are 2 pairs of data that are closer to each other in terms of back scattering values:

Sigma0_VH_09May2017_mst_db: -8.51345 intensity_db
Sigma0_VH_27May2017_slv1_db: -19.66345 intensity_db
Sigma0_VH_14June2017_slv2_db: -7.75498 intensity_db
Sigma0_VH_02July2017_slv3_db: -21.21673 intensity_db

The pixel data that I extracted the values is a forest area. How can these data differ so much in terms of dB values and which one that I can trust?

#2

Soil moisture and canopy moisture influence the backscatter a great deal. In other words, that is normal and you can trust all of the values.

#3

Can you share with us your processing steps?

#4

Hello,
I am also interested in your processing steps.
What is the best way to perform a reliable change detection on Sentinel 1 product?
I see there is a change detection in SNAP menu, how to interpret it? can anyone point to some litteratures I can read?

#5

Can it be due to speckle noise?
Instead of informing single pixel values, it would be better to trust in mean values of an homogeneous area.

#6

Hi, Yes certainly using a homogeneous area will give a much more representative radar cross-section than using an individual pixel (due as you say to speckle). You should then obtain similar RCS values from the four date.